/Engine/Plugins/Runtime/MeshModelingToolset/Source/MeshModelingTools/Public/EditMeshPolygonsTool.h
FPolyEditActivityStartChangeis used to cancel out of an active action on Undo. No action is taken on Redo, ie we do not re-start the Tool on Redo.
class FPolyEditActivityStartChange : public [FToolCommandChange](API\Runtime\InteractiveToolsFramework\FToolCommandChange)
int32
ActivityTimestamp
bool
bHaveDoneUndo